... I already run
four instant messaging clients on my laptop. A single client would be
nice, but it's not that important. Once we finally learn how
availability should work from an existing player like Skype or from an
entirely new overlay network (as Skype was a few years ago), then we
can worry about consolidation.

Now I'm not so sure.

Who will aggregate this flood for me, in some convenient and semantically meaningful way?